Methodologies for Plasmopara halstedii Research

Abstract

The objective of this work was to find practical procedures to overcomemethodological drawbacks encountered during studies on sunflower downy mildew.Techniques for recovering living isolates of Plasmopara halstedii from the fieldand for the preservation of infected leaf samples for furthermolecular analysis weredeveloped. A Polymerase Chain Reaction (PCR)-based test for the detection of P.halstedii in sunflower leaves and a method to remove azoxystrobin from fungicidetreatedseeds are proposed. In situ-inoculations of pre-germinated seeds allowedthe recovery of living isolates from the field. Three sample-preservation methodswere evaluated (silica, heating and lyophilization) resulting in high yield andquality of the DNA extract. It was detected the presence of the pathogen insymptomless leaves through PCR using molecular markers based on expressed sequence tags. A treatment using sodium hypochlorite is recommended for theremoval of azoxystrobin from fungicide treated seeds.